Radiographic measures of pelvic limb malalignment in small breed dogs with various grades of medial patellar luxation

The aim of the present study was to provide radiological measures of pelvic limb deformity in dogs from small breeds with medial patellar luxation (MPL) of various grades by means of some anatomical and mechanical angles of the femur and the tibia. The study was performed with 87 dogs (174 joints) from four small breeds: Mini-Pinscher, Chi-hua-hua, Yorkshire Terrier and Pomeranian. Out of them, 53 dogs were diagnosed with various grades of MPL and the other served as healthy controls. Six femoral angles, eight tibial angles and quadriceps angle were measured in dogs affected by grades I–III MPL and in healthy controls. On the basis of the studied dogs from small breeds, it was found out that as MPL grade increased, distal anatomical and mechanical femoral angles increased proportionally with significant difference vs angles in dogs non-affected by MPL. Proximal femoral angles did not change with MPL grade. Tibial angles showed significant changes, characterised with increase in proximal angles as MPL advanced, while distal tibial angles showed a negative relationship with MPL grade. On the basis of our results, we suggest that angles with clinical relevance for evaluation of canine patients with medial luxation of the patella are the anatomical and mechanical lateral distal femoral angles (aLDFA, mLDFA), the femoral anteversion angle (FVA) and the mechanical medial proximal tibial angle (mMPTA). © 2018, Springer-Verlag London Ltd., part of Springer Nature.